Modelling of heat transfer in internal combustion engines with variable density effect

Heat transfer is one of the major factors affecting the performance, efficiency, and emissions of internal combustion engines. As convection heat transfer is dominant in engine heat transfer, accurate modelling of the boundary layer heat transfer is required. In engine computational fluid dynamics (CFD) simulations, the wall function approach has been widely used to model the near-wall flow and temperature field. The present paper suggests a modified wall function approach to model heat transfer in internal combustion engines. Special emphasis has been placed on introducing the effect of variable density and variable viscosity in the model formulation. A non-dimensional temperature corrector is suggested to incorporate the variable density effect on the wall function approach. The suggested model is applied in KIVA-3V and is validated against experimental data of a homogeneous charge compression-ignition engine, showing improved predictions for pressure and emissions compared with the standard wall function model.